Membrane thickness has significant effect on permeability of membrane.In this work the membrane thickness gradient of isoflux ceramic membrane was calculated with the Navier-Stokes and Darcy equations

which governed the bulk flow and the flow through the membrane

respectively.The specific resistance of porous medium was calculated by Konzey-Carmen equation.The results showed that the membrane thickness was approximately linear to the distance in axial direction.The cross-flow velocity had a significant influence on the membrane thickness gradient along the axial direction

so it is necessary to choose different membrane thickness gradient along the axial direction to obtain uniform trans-membrane pressure at different cross-flow velocity.The effects of pressure and temperature were relatively insignificant.The result of this study may provide guidance on membrane preparation and application.